WO2010129669A1

WO2010129669A1 - Compressible fluid control system valve positioner isolation apparatus and method

Info

Publication number: WO2010129669A1
Application number: PCT/US2010/033723
Authority: WO
Inventors: Richard James Colony; Victor D. Bruzas; John Leslie Rodgers Iv
Original assignee: Siemens Industry Inc
Current assignee: Siemens Industry Inc
Priority date: 2009-05-08
Filing date: 2010-05-05
Publication date: 2010-11-11
Anticipated expiration: 2011-11-08

Abstract

Valve positioner isolation apparatus (40) and methods facilitate isolation of one or more compressible fluid control circuits (S, O1, O2, e.g., in pneumatic control systems) from their associated valve positioner (80), so that compressible fluid flow properties therein can be maintained during valve positioner maintenance or replacement. Isolation of the valve positioner (80) from associated control circuits (S, O1, O2) de couples the valve positioner from any associated energization sources. Isolation thereby accomplishes the need to de energize all potential energy sources coupled to the valve positioner without shutting down all ongoing processes associated with the control circuit. Associated lockout features (90, 92, 93) of the present invention, in cooperation with the isolation valve (60, 60', 60"), inhibit unauthorized access and change of the isolation valve operational status.

Description

COMPRESSIBLE FLUID CONTROL SYSTEM VALVE POSITIONER ISOLATION APPARATUS AND METHOD

[0001] CLAIM TO PRIORITY

[0002] This application claims the benefit of our co-pending United States provisional patent application entitled "Pneumatic Isolation Device for Valve Positioners" filed May 8, 2009 and assigned serial number 61/176,619, which is incorporated by reference herein.

[0003] BACKGROUND OF THE DISCLOSURE

[0004] 1. Field of the Invention

[0005] The invention relates to compressible fluid control systems, including pneumatic control systems, which utilize valve positioners to operate actuators by regulating fluid flow properties, such as flow rate or pressure. The present invention relates more particularly to methods and apparatus to isolate a valve positioner from its associated control circuits, so that the valve positioner can be removed from the system while maintaining pre-isolation fluid flow properties in the control circuits. By utilizing the present invention, a valve positioner can be removed for repair or replacement while maintaining operational status quo in the associated control circuits, without the need to shut down the entire control system. [0006] 2. Description of the Prior Art

[0007] Pneumatic control systems, as well as control systems employing compressible fluid media other than air, employ control circuits with actuators that perform control functions. Actuators can regulate operation of remote devices in manufacturing or other process control environments in response to changes in the fluid properties within the control circuit that are regulated by a valve positioner. In typical pneumatic control environments, an actuator is responsive to changes in pneumatic pressure or airflow rate initiated by the valve positioner. Such a typical pneumatic control environment provides a pressurized air supply upstream of the valve positioner. Downstream the valve positioner there are often one or two control circuits coupled to the associated actuator. A bi-directional actuator has a piston, diaphragm or the like pressure transducer that moves in response to variations in pressure supplied from respective control circuits on either or both sides of the transducer. In a single-direction actuator pressure is supplied by a single control circuit to one side of the transducer against counter-biasing force of a spring or other biasing element.

[0008] When servicing or replacing a valve positioner, the service technician first shuts down all existing and potential energy sources that are coupled to the positioner. In a typical pneumatic control system this would include all control circuits coupled to the positioner that potentially might contain pressurized air: the upstream air supply as well as related downstream single- or bi-directional actuators that are controlled by the valve positioner. This necessitates placing all related upstream and downstream control circuits at ambient or zero gauge - pressure: effectively shutting down the control system operation. In a factory or other working process control environment, this results in complete shut-down of the controlled environment. In many control environments, it would be preferable to maintain the operational status quo of each compressible fluid state in each control circuit (for example maintaining air pressure at an existing assigned level within a downstream pneumatic actuator circuit, so that an associated valve maintains a designated flow rate within a controlled process) rather than shut down the related portion of the factory.

[0009] In addition to shutting down energy in each control circuit prior to valve positioner servicing, the service technician locks out each control circuit to prevent unauthorized re-energization during the servicing operations. To this end, lockout devices are provided for each control circuit between the potential energy source and the valve positioner. Often such a lockout device comprises a form of lockable shut-off valve to which the technician applies a servicing lock that prevents unauthorized change in the associated lockout valve status (e.g., unauthorized re-pressurization of the associated control circuit) . The lockout device requires installation and ongoing maintenance of additional components within the control circuit. Each circuit requires a separate lockout device and associated lock, necessitating inspection and confirmation of locked-out status of multiple lockout devices for^' each serviced valve positioner.

[0010] Thus, a need exists in the art for a valve positioner isolation apparatus and method that facilitates isolation of compressible fluid control circuits associated with a valve positioner, so that status quo operational condition of each such circuit can be maintained during valve positioner maintenance or replacement, without need to shut down related control circuits to zero pressure or fluid flow condition.

[0011] An additional desirable and complimentary need exists for a valve positioner isolation apparatus and method that facilitates simultaneous isolation of a plurality of, and more desirably, all control circuits coupled to a valve positioner, so that the entire valve positioner is isolated from all associated control circuits by a single operational step.

[0012] An additional desirable and complimentary need exists for a valve positioner isolation apparatus and method that facilitates lockout of the valve positioner during servicing operations, and preferably prevents unauthorized change of isolation status of the control system.

[0013] SUMMARY OF THE INVENTION

[0014] Accordingly, an object of the present invention is to create a valve positioner isolation device that facilitates maintenance or replacement of a valve positioner without shutting down control circuits that are coupled to the valve positioner.

[0015] Another desirable and complimentary, but not required, object of the present invention is to create a valve positioner isolation device that isolates a plurality, and even more desirably, all control circuits that are coupled to the valve positioner.

[0016] Another desirable and complimentary, but not required, object of the present invention is to create a valve positioner isolation device that selectively locks out one or more, and even more desirably all control circuits that are coupled to the valve positioner during valve positioner maintenance or replacement operations. An associated, but not required object is ability to prevent unauthorized change of valve positioner isolation status by optional use of a locking device during all operational modes of the valve positioner and associated control system.

[0017] These and other objects, alone or in any combination, are achieved in accordance with the present invention by the valve positioner isolation apparatus and methods of the present invention, that facilitate isolation of one or more control circuits from their associated valve positioner, so that compressible fluid flow properties therein can be maintained during valve positioner maintenance or replacement. Isolation of the valve positioner from associated control circuits de-couples the valve positioner from any associated energization sources. Isolation thereby accomplishes the need to de-energize all potential energy sources coupled to the valve positioner without shutting down all ongoing processes associated with the control circuit. Therefore, by maintaining status quo operating properties within a control circuit during service of the associated valve positioner, there is no need to shut down the related operations in the associated process control system (e.g., a factory shut down of the affected processes). Associated lockout features of the present invention, in cooperation with the isolation valve, inhibit unauthorized access and change of the isolation valve operational status.

[0018] One aspect of the present invention is a compressible fluid control system comprising a plurality of compressible fluid control circuits. A valve positioner is in fluid communication with each respective control circuit, for regulating fluid flow properties therein. An isolation valve is interposed between each respective control circuit and the valve positioner, having a first operational state that is capable of enabling fluid communication between each respective control circuit and the valve positioner, and a second operational state capable of isolating respective fluid communication there between, while maintaining pre-isolation fluid flow properties in at least one of the control circuits. Isolation valves for a plurality or all of the control circuits optionally may be configured for simultaneous operation in common operational states. The isolation valves for a plurality or all of the control circuits optionally may be incorporated in a common manifold interposed between the valve positioner and the associated control circuits .

[0019] Another aspect of the present invention is directed to a compressible fluid control system having a plurality of compressible fluid control circuits, and a valve positioner for regulating fluid flow properties within each respective control circuit in fluid communication therewith, and more particularly to a method for selectively isolating fluid communication there between. The method comprises providing an isolation valve interposed between each respective control circuit and the valve positioner, having a first operational state capable of enabling fluid communication between each respective control circuit and the valve positioner, and a second operational state capable of isolating respective fluid communication there between; selectively placing the isolation valve in the first operational state; and selectively placing the isolation valve in the second operational state, while maintaining pre-isolation fluid flow properties in the respective control circuits. Optionally a plurality or all of the control circuits may be simultaneously in communication with or isolated from the isolation valve in tandem. Optionally one or more of the isolation valves may be locked in a desired operational state with a lockout device.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompany.ing drawings, in which:

[0022] FIG. 1 shows an exploded view of the compressible fluid control system of the present invention in an exemplary industrial process control environment;

[0023] FIG. 2 is a fluid schematic of the present invention in a control circuit for a bi-directional actuator;

[0024] FIG. 3 a partial fluid schematic of the present invention, showing a single-direction actuator embodiment;

[0025] FIG. 4 is a front elevational perspective view of the present invention disconnected from associated control circuits;

[0026] FIG. 5 is a rear elevational perspective view of the invention of FIG. 4;

[0027] FIGs. 6 and 7 are cross-sectional elevations of the invention of FIG. 4, showing the isolation valve thereof in respective closed and open positions;

[0028] FIG. 8 is a front elevational perspective view similar to FIG. 4, showing lockout covers;

[0029] FIGs. 9-11 show an alternative embodiment of a rotary lockout valve; and [0030] FIGs. 12-13 show a fragmentary elevational view an alternative embodiment of a linear motion lockout valve.

[0031] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. Like or alternative constructions of elements are sometimes designated herein with the prime symbol (e.g., 60, 60' or 60") .

[0032] DETAILED DESCRIPTION

[0033) After considering the following description, those skilled in the art will clearly realize that the teachings of my invention can be readily utilized in a compressible fluid control system by providing an isolation valve between a valve positioner and related control circuit. Desirably a plurality or all of the control circuits may be isolated simultaneously from the valve positioner with the isolation valve. The isolation valve optionally may be utilized in conjunction with a lockout device to prevent unauthorized access to the isolation valve operational setting.

[0034] General Control System Schematic and Operation

[0035] Referring generally to FIGs. 1-3, the compressible fluid control system of the present invention is depicted in an exemplary pneumatic control system 20 environment. It should be understood by those skilled in the art that other types of compressible fluid other than air may be utilized as an energy transfer medium within the system.

[0036] In FIGs. 1 and 2, compressed air within the control system 20 control circuits S, 01 and 02 is in communication with a known actuator 30. The exemplary actuator 30 in FIGs. 1 and 2 is a bi-directional type that is used to regulate flow within a pipe of a controlled process. As can be appreciated to those skilled in the art, the actuator 30 includes a pair of chambers 32 and 35 with a diaphragm, piston or the like 34 that translates in response to the differential pressure between Pi and P₂ provided by respective associated control circuit lines 01 and 02. Diaphragm 34 translation in turn causes translation of the shaft 36 along axis A, thereby generating the mechanical force needed to change actuation status of the ultimately controlled device within the controlled industrial process (e.g., to open, close or regulate partial throttling of a supply pipe within an industrial process) .

[0037] While pressure differential-drive linear translation of shaft 36 is shown in FIG. 2, it should be understood that all other types of known actuators including those employing rotary motion, turbines and flow rate rather than pressure differential driving power may be practiced within the teachings of the present invention. Referring to FIG. 3 an alternative single-direction actuator 30" is shown that has a single pressurized chamber 32", which causes translation of the piston 34" as a function of the pressure differential between pressurized air P₁ supplied by control circuit 01' and the resetting biasing force F_ε3τ generated by biasing springs 37' . The pressure P_Aτv in the spring chamber is understood to be localized atmospheric pressure that is vented to ambient air or via a return blow-off line 02 (not shown) .

[0038] Differential pressure within the exemplary actuator 30 of FIGs. 1 and 2 is regulated by a known valve positioner 80 that is interposed between a pressurized air supply 38 and the actuator control circuits 01, 02. Isolation manifold 40 includes a manifold body 42 that is coupled to the valve positioner 80. The manifold body defines internal ports 4S, 401 and 402 that are respectively coupled to and in fluid communication with the control circuits S, 01 and 02. Valve positioner 80 receives compressed air from the supply 38 via port 4S and throttles it to lower pressures Pj, P_> that are routed to the respective control circuits 01, 02 via ports 401 and 402 (assuming for simplified presentation herein that the control circuits 01, 02 experience little or minimal relative pressure losses) .

[0039] As shown in FIGs. 1 and 2, isolation valve 60 is interposed between the valve positioner 80 ports 4S, 401, 402 and the respective control circuits S, 01 and 02. The valve 60 is shown as a linearly actuated spool valve assembly having corresponding valves VS, VOl, V02 for each control circuit. One, a plurality, or advantageously all of the valves VS, VOl and V02 of the spool valve assembly 60 may be independently or simultaneously controlled as a matter of design choice. However, in field applications, simultaneous actuation of all isolation valves associated with control circuits coupled to the valve positioner 80 allows the service technician to isolate the valve positioner from the entire control system with minimal effort. To this end, the exemplary isolation valve assembly embodiment 60 of FIGs. 1 and 2 is shown as an integrated structure that controls all related control circuit valves in a single actuation. Other isolation valve assembly embodiments will be described below, it being understood that one skilled in the art may choose any valve design^' that performs the intended isolation functions of the present invention that are described herein.

[0040] Isolation manifold 40 is shown in greater detail in FIGs. 4-3. The manifold body 42 is an interface component between the valve positioner 80 and the related control circuits S, 01 and 02. Valve positioner 80 abuts against a front engagement surface of the manifold body 42; a fluid seal between those components is maintained by exemplary o-rings 43 that circumscribe each of the ports 4S, 401 and 402 on the front engagement surface. The manifold is in fluid communication with respective control circuits S, Ol and 02 via threaded outlets 44, 45, 46 for mating with corresponding male fluid fittings of the control circuits. Alternative known fluid connection to the control circuits may be accomplished by quick-disconnect fittings (not shown) . Alternatively, the manifold may be directly coupled to an actuator, thereby eliminating the need for external control circuit lines or tubing. [0041] Optionally each control circuit, or any sub-combination thereof, may incorporate pressure gauges GS, GOl, GO2 that may be coupled directly to the manifold body 42.

[0042] The isolation valve assembly spool valve 60 embodiment is shown in respective closed and open positions in FIGs. 6 and 7. In FIG. 6 the spool valve 60 has a shaft 62 with respective end stops 63, 64 that limit linear motion of the valve assembly. Shaft 62 has necked portions 66, 67 and 68 with paired o-rings 65 axially displaced above and below each necked portion, for preservation of fluid sealing properties in each separate control circuit. In FIG. 6 the valve is in a closed position when the neck portions are axially displaced from respective pairs of ports and control circuits S-44-4S, 01-45-401 and 02-46-402. In FIG. 7 the necked portions 66, 67, and 68 are aligned with their respective pairs of ports and control circuits, enabling fluid communication across the isolation valve 60.

[0043] As shown in FIGs. 6-8, the isolation valve shaft 62 defines recesses 70, 72 for receipt of a lockout pin 90. When the pin is selectively inserted in one of the recesses, the isolation valve 60 is locked in it chosen open or closed position, thereby preventing unauthorized change of isolation status. Pin ring 91 may be attached to the pin 90 for ease of insertion or removal. The pin circumference may include a threaded portion for threaded insertion into mating threads formed in the manifold body 42 for secure affixation. A lockout cap 92 may be provided to inhibit unauthorized access to the locking pin 90, so that the isolation valve may be maintained in either closed or open operational status at the choice of the field technician. During field servicing repair or replacement of the valve positioner 80, the field technician may secure a lock 93 to the lockout cap 92, using known techniques. Additional covers 94, 96 may provided on the ends of the isolation valve 60 for weather or other environmental protection purposes.

[0044] FIGs. 9-11 show an alternative embodiment of isolation valve 60' employing rotary on-off motion. FIGs. 12 and 13 are fragmentary elevational views of a cage-type linear isolation valve 60". As those skilled in the art will understand, the cage valve 60" has a generally annular outer cage 6OA" having radially staggered ports that mate with corresponding manifold ports 4S and control circuit S. O-rings 65" are oriented above and below each port/control circuit. A necked reciprocating valve 60" is translated to align a necked portion with each respective port/control circuit to establish fluid communication when the valve is open.

[0045] Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.

Claims

What is claimed is:

1. A compressible fluid control system (20) comprising: a plurality of compressible fluid control circuits (S, 01, 02); a valve positioner (80) in fluid communication with each respective control circuit, for regulating fluid flow properties therein; an isolation valve (60) interposed between each respective control circuit and the valve positioner, having a first operational state capable of simultaneously enabling fluid communication between each respective control circuit and the valve positioner, and a second operational state capable of simultaneously isolating respective fluid communication there between while maintaining pre-isolation fluid flow properties in at least one of the control circuits.

2. The system of claim 1, further comprising an isolation manifold (42) having: a plurality of manifold passages (4S, 401, 402) capable of forming portions of respective control circuits (S, 01, 02); an engagement surface capable of coupling of a valve positioner (80) thereto, and capable of establishing fluid communication between the valve positioner and each of the respective manifold passages; and a cavity interposed between the engagement surface and each of the respective manifold passages, having the isolation valve (60) therein, the isolation valve first operational state simultaneously enabling fluid communication between each respective manifold passage and the valve positioner, and a second operational state simultaneously isolating respective fluid communication there between while maintaining pre-isolation fluid flow properties in at least one of the manifold passages.

3. The system of claim 2, wherein a first one of the manifold passages (4S) is capable of being coupled to a compressible fluid supply (38) and second one of the manifold passages (401) is capable of being coupled to a compressible fluid control circuit (01) regulating one direction of directional flow actuator (30) operation.

4. The system of claim 3, wherein a third one of the manifold passages (402) is capable of being coupled to a compressible fluid control circuit regulating (02) a second direction of bi-directional flow actuator (30) operation.

5. The system of claim 2, wherein the manifold passages (4S, 401, 401) are adapted for connection to threaded fluid fittings (44, 45, 46) forming respective portions of the control circuits.

6. The system of claim 5, wherein the fluid fittings are quick-disconnect fluid fittings.

7. The system of claim 1, wherein the isolation valve (60) is selected from the group consisting of linear valves, spool valves, poppet valves and rotational valves.

8. The system of claim 1, further comprising a lockout mechanism (90) coupled to the isolation valve (60, 70, 72) for preventing change of operational states thereof.

9. The system of claim 8, wherein the lockout mechanism includes a pin (90) selectively engageable with the isolation valve (60, 70, 72) for prevention of isolation valve movement.

10. The system of claim 9, further comprising a cover (92) for covering the pin.

11. The system of claim 8, wherein the lockout mechanism (60, 70, 72, 90) is capable of selectively engaging the isolation valve in either operational state.

12. The system of claim 8, wherein the lockout mechanism includes a cover (92, 94, 96) for covering at least a portion of the isolation valve (60) .

13. In a compressible fluid control system (20) having a plurality of compressible fluid control circuits (S, 01, 02), and a valve positioner (80) for regulating fluid flow properties within each respective control circuit in fluid communication therewith, a method for selectively isolating fluid communication there between, comprising: providing an isolation valve (60) interposed between each respective control circuit and the valve positioner, having a first operational state capable of simultaneously enabling fluid communication between each respective control circuit and the valve positioner, and a second operational state capable of simultaneously isolating respective fluid communication there between; selectively placing the isolation valve in the first operational state; and selectively placing the isolation valve in the second operational state, while maintaining pre-isolation fluid flow properties in the respective control circuits.

14. The method of claim 13, further comprising removing the valve positioner (80) after placing the isolation valve (60) in the second operational state, while maintaining pre-isolation fluid flow properties in isolated portions of the respective control circuits (S, 01, 02) . -

15. A compressible fluid control system (20) comprising: a plurality of compressible fluid control circuits (S, 01, 02); a valve positioner (80) in fluid communication with each respective control circuit, for regulating fluid flow properties therein; means for isolating fluid communication between the valve positioner and the respective control circuits (60, 60', 60"), interposed there between, the means having a first operational state capable of simultaneously enabling fluid communication between each respective control circuit and the valve positioner, and a second operational state capable of simultaneously isolating respective fluid communication there between while maintaining pre-isolation fluid flow properties in at least one of the control circuits.

16. A compressible fluid control system comprising: an isolation manifold having (40, 42) : a plurality of manifold passages (4S, 401, 402) formed therein, capable of being coupled to respective control circuits (S, 01, 02) ; an engagement surface capable of coupling of a valve positioner (80) thereto, and capable of establishing fluid communication between the valve positioner and each of the respective manifold passages; and an isolation valve (VS, VOl, V02, 60, 60', 60") interposed between each respective manifold passage and the valve positioner, each isolation valve having a first operational state capable of enabling fluid communication between each respective manifold passage and the valve positioner, and a second operational state capable of isolating respective fluid communication there between while maintaining pre-isolation fluid flow properties in at least one of the manifold passages.

17. The system of claim 16, wherein a first one of the manifold passages (4S) is capable of being coupled to a compressible fluid supply (38) and second one of the manifold passages (401) is capable of being coupled to a compressible fluid control (01) circuit regulating one direction of directional flow actuator (30) operation.

18. The system of claim 17, wherein a third one of the manifold passages (402) is capable of being coupled to a compressible fluid control circuit (02) regulating a second direction of bi-directional flow actuator (30) operation.

19. The system of claim 16, wherein the isolation valve (60, 60', 60") is selected from the group consisting of linear valves, spool valves, poppet valves and rotational valves.

20. The system of claim 16, wherein the manifold passages (4S, 401, 402) are adapted for connection to threaded fluid fittings (44, 45, 46) forming respective portions of the control circuits.

21. The system of claim 16, further comprising a lockout mechanism (90) coupled to the isolation valve (60, 70, 72) for preventing change of operational states thereof.

22. The system of claim 21, wherein the lockout mechanism includes a pin (90) selectively engageable with the isolation valve (60, 70, 72) for prevention of isolation valve movement.

23. The system of claim 22, further comprising a cover (92) for covering the pin (90) .

24. The system of claim 21, wherein the lockout mechanism (60, 70, 72, 90) is capable of selectively engaging the isolation valve (60) in either operational state.

25. The system of claim 21, wherein the lockout mechanism includes a cover (92, 94, 96) for covering at least a portion of the isolation valve.

26. The system of claim 16, wherein the respective isolation valves (VS, VOl, VO2) are coupled (60, 60' , 60") for common tandem switching between operational states.